Try Penetrol .... you can pick up a can from a good paint store. cost about $10. Clean your boat first then apply Penetro with a old clean rag then wipe dry. Easy to put on and doesn't required a lot of elbow grease! You will be very pleased! Let me know what you think...

I used the 3M Fiberglass Cleaner and Wax on my '73 H16 and my friend's '79 Spirit 21 with a power buffer. Worked GREAT. The hulls (all 3 of them) look awesome. Just be sure to follow the directions on the bottle - don't let the stuff dry... just keep working it in until it all comes off; so do one small area at a time. I didn't read the directons carefully at first and I did a big part of the hull and tried to take it off again - man that stuff is HARD to get off after it dries. Just FYI.

The best product I've found is Aqua-buff. It produces the best finish even from old chalky gel coat. If your hull is very chalky you need to use the 1000w then the 2000w to get the best finish. Just make sure you keep the product wet while you buff. After buffing and washing just protect your hull with any good wax. Many in the high performance power boat world use this product. It was recommended to my by one of the top grafixs painters in the country. It doesn't leave anything on the boat like the Penetrol product. It's purely a compound that leave a swirl free finish and is much easier to use then the 3M compounds.

Found a can of Penetrol in the closet and applied some to my 1981, dry-hulled 16... after scrubbing her real well, of course. Man-ole-man what a difference! I also used it to shine up the mast and boom and WOW!! After rubbing it all over my wife the can got knocked over so i can't report on the deck furniture as i had hoped. Penetrol really does the job and is recommended for fiberglass on the can.